Late Oligocene (?). (In: Stratigraphy of Mesozoic and Cenozoic Periods of Western Siberian Lowland. E.A.Filippova, editor)
Reference:
Filippova,E.A. (1957)
Late Oligocene (?). (In: Stratigraphy of Mesozoic and Cenozoic Periods of Western Siberian Lowland. E.A.Filippova, editor) Gosudarstyy Soyuznyy Zapadno-Sibirskiy Nefterazvedochnyy Trest,Moskv,State Union Western-Siberian Petroleum Survey Trust.(Moscow)
P. 133- 135